The present invention relates to an electrode plate including metal electrodes with gaps therebetween filled with a resin, a process for producing the electrode plate, a liquid crystal device including the electrode plate, and a process for producing the liquid crystal device.
Electrode plates conventionally used in liquid crystal devices of, e.g., a twisted nematic (TN)-type and a super twisted nematic (STN)-type generally comprise a glass substrate and transparent electrodes of ITO (indium-tin-oxide), etc., formed thereon. However, such transparent electrodes have a fairly high resistivity so that they have caused a problem of voltage waveform deformation due to electrical signal delay along with increases in size and resolution of the display area. This problem is particularly noticeable in the case of a liquid crystal device using a ferroelectric liquid crystal due to a smaller cell gap.
In order to solve the problem, it may be possible to increase the thickness of the transparent electrodes, but the formation of such thick transparent electrodes requires increased time and cost and results in a lower transparency of the electrodes.
In order to solve the above-mentioned problems, it has been practiced to form a metal electrode along a transparent electrode of a small thickness (as disclosed in Japanese Laid-Open Patent Application (JP-A) 2-63019). According to the practice, an electrode plate having metal electrodes thereon embedded with a transparent insulating material is provided, and transparent electrodes of ITO film, etc., are formed thereon so as to be electrically connected with the corresponding metal electrodes, respectively, via through-holes in the insulating material.
In producing an electrode plate having a structure as described above, it has been also proposed to use a transparent resin as the insulating material filling the gaps between the metal electrodes (e.g., JP-A 6-347810 and JP-A 8-304842) as illustrated in FIGS. 23 to 25.
According to the proposed process, as shown in FIG. 23A, on a smooth or smoothening mold substrate (hereinafter called xe2x80x9csmooth platexe2x80x9d) 100, a prescribed amount of a liquid resin of ultraviolet (UV)-curable resin 101 is placed dropwise by using a dispenser (not shown). Then, as shown in FIGS. 23B and 23C, a glass substrate 104 already provided with a pattern of ca. 1 xcexcm-thick metal electrodes 103 is placed thereon so that the surface thereof provided with the metal electrodes 103 contacts the liquid resin 101.
Further, as shown in FIGS. 24A and 24B, the smooth plate 100 and the substrate 104 are pressed to each other to ensure an intimate contact over the entire area by pressing with a press 105. In this step, in order to ensure a good contact and electrical conductance between the metal electrodes 103 and corresponding transparent electrodes formed in a later step, the smooth plate 100 and the substrate 104 are caused to come in contact with each other strongly and uniformly over the entire area so as to remove the UV-curable resin 101 from the metal electrode surface completely or to the extent that a very small amount of the resin 101 remains on a part of the metal electrode surface.
Thereafter, the substrate 104 in contact with the smooth plate 100 is taken out from the press 105 and is irradiated with UV rays 106 from the substrate side by using a mask (not shown) disposed in a peripheral region of the substrate 104 to cure the UV-curable resin 101, as shown in FIG. 25A. Then, the smooth plate 100.is removed from the substrate 104 by using a peeling unit (not shown), followed by ultrasonic cleaning in, e.g., isopropyl alcohol (IPA) to remove the uncured resin, thus obtaining an electrode plate 107 having thereon a plurality of metal electrodes 103 and a UV-cured resin 101 filling the gaps between the metal electrodes 103, as shown in FIGS. 25B and 25C.
In the above-described production process of the electrode plate, however, as shown in FIG. 24B, a part 101a of the UV-curable resin 101 flows out or is squeezed out from the side (edge) portions between the smooth plate 100 and the glass substrate 104 under pressure in the pressing (or resin-filling) step. In such a state, even when the smooth plate 100 and the glass substrate 104 are further pressed against each other by further increasing an applied pressure by means of the press 105, the UV-curable resin 101 disposed therebetween is not extended or expanded any longer. As a result, a part of the gaps between the metal electrodes 103 is not filled or is partially filled with the UV-curable resin 101 to result in an uneven surface portion, thus being liable to cause adhesion (or contact) failure between the metal electrodes and associated transparent electrodes, respectively, in a later step.
Further, the flowing-out part 101a of the UV-curable resin 101 as described above is attached to and contaminates the press 105, thus leading to dirt when such a press 105 is repetitively used. Consequently, a production yield of the electrode plate is liable to be lowered.
In view of the above-mentioned problems, a principal object of the present invention is to provide an electrode plate improved in uniformity and flatness (or planarity) of a resin filling gaps between metal electrodes formed on a substrate and capable of preventing contamination due to flowing-out of the resin, thus enhancing a product yield, and a liquid crystal device including such an electrode plate.
Another object of the present invention is to provide processes for producing an electrode plate and a liquid crystal device as described above.
According to the present invention, there is provided an electrode plate, comprising: a substrate, a plurality of metal electrodes formed with gaps therebetween in a prescribed pattern on the substrate, and a resin filling the gaps; wherein
the substrate is provided with an elongated projection disposed in a peripheral region thereof.
According to another aspect of the present invention, there is provided a process for producing an electrode plate comprising the steps of:
forming on a substrate a plurality of metal electrodes with gaps therebetween in a prescribed pattern,
forming an elongated projection in a peripheral region of the substrate,
placing a resin between the substrate and a mold substrate, and
filling the gaps with the resin by pressing within a region inside said elongated projection.
According to another aspect of the present invention, there is also provided a process for producing an electrode plate comprising the steps of:
forming on a substrate a plurality of metal electrodes with gaps therebetween in a prescribed pattern,
forming an elongated projection in a peripheral region of a mold substrate,
placing a resin between the substrate and the mold substrate, and
filling the gaps with the resin by pressing within a region inside said elongated projection.
According to a further aspect of the present invention, there is provided a liquid crystal device, comprising: a pair of oppositely disposed plates, and a liquid crystal disposed between the plates; at least one of the plates having an electrode plates comprising:
a substrate, a plurality of metal electrodes formed with gaps therebetween in a prescribed pattern on the substrate,:and a resin filling the gaps, and a plurality of transparent electrodes each electrically connected with an associated metal electrode; wherein
the substrate is provided with an elongated projection disposed in a peripheral region thereof.
According to a still further aspect of the present invention, there is provided a process for producing a liquid crystal device in which a liquid crystal is disposed between a pair of oppositely disposed plates including at least one electrode plate comprising: a substrate, a plurality of metal electrodes formed with gaps therebetween on the substrate, a resin filling the gaps, and a plurality of transparent electrodes each electrically connected with an associated metal electrode; the process comprising the steps of:
forming on a substrate a plurality of metal electrodes with gaps therebetween in a prescribed pattern,
forming an elongated projection in a peripheral region of the substrate, and
filling the gaps with the resin within a region inside said elongated projection.
According to a still further aspect of the present invention, there is also provided a process for producing a liquid crystal device in which a liquid crystal is disposed between a pair of oppositely disposed plates including at least one electrode plate comprising: a substrate, a plurality of metal electrodes formed with gaps therebetween on the substrate, a resin filling the gaps, and a plurality of transparent electrodes each electrically connected with an associated metal electrode; the process comprising the steps of:
forming on a substrate a plurality of metal electrodes with gaps therebetween in a prescribed pattern,
forming an elongated projection in a peripheral region a mold substrate,
placing a resin between the substrate and the mold substrate, and
filling the gaps with the resin by pressing within a region inside said elongated projection.
When a resin filling gaps between metal electrodes formed on a substrate is flattened or smoothed by pressing, it is very difficult to accurately control an appropriate amount of the resin supplied for forming a smooth and even surface, so that a part of the resin pressed between the substrate and a mold (smooth) plate is liable to be squeezed out from the sides of the substrate to cause an irregularly filled portion (unfilled or partially filled portion) of the resin as described above.
We have found that the gaps between metal electrodes are effectively filled with the resin with a good uniformity and planarity in a pressing step by providing an elongated projection in a peripheral region of a substrate or a mold plate.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings, wherein identical parts or members are denoted by identical reference numerals, unless otherwise noted expressly.